A known polygon mirror made of plastic and having six reflecting surfaces typically has three projections (first contact portions) on an upper surface thereof at positions corresponding to three vertices selected from the six vertices of the upper surface. The polygon mirror is fastened to a light deflector using a pressing member, by which the projections of the polygon mirror are pressed toward a motor.
The polygon mirror made of plastic would deform when it is pressed by the pressing member. In the above configuration of the polygon mirror, as the amount of deformation varies depending on whether or not the vertex is provided with the projection, each of the reflecting surfaces deforms by a different amount.
In view of the above, it is a first object to provide a polygon mirror which can prevent the reflecting surfaces from deforming by different amounts, and to provide a light deflector comprising such a polygon mirror.
The polygon mirror made of a plastic resin may be manufactured by a known method, in which a plastic resin is injected through a gate provided at a center of the mold.
However, in a case where the polygon mirror has a recessed portion into which a motor for rotating the polygon mirror is inserted, the thickness of the polygon mirror is reduced at a portion corresponding to the recessed portion than at other portions. Therefore, the liquidity of the resin decreases, when molding, at the portion corresponding to the recessed portion with the result that the moldability of the polygon mirror may deteriorate.
In view of the above, it is a second object to provide a polygon mirror which improves moldability.
Generally, a polygon mirror has a plurality of reflecting surfaces, by which a light beam emitted from a light source is reflected toward a scanning optical system when the polygon mirror rotates at high speeds.
The polygon mirror is shaped such that two adjacent reflecting surfaces are directly connected to form a sharp edge. This causes the mold releasing resistance to be increased when the molded product is removed from the mold. As a result, the moldability of the polygon mirror deteriorates.
In view of the above, it is a third object to provide a polygon mirror which improves moldability by reducing the mold releasing resistance.